Soft Bounce Failures

Soft bounce failures occur when email messages are processed by recipient mailbox provides but are returned as undeliverable before they reach their recipients. These failures are a normal part of bulk email sending because mailbox providers can defer messages if they are unable to process them during the intial attempts at delivery.

Note: To retry a message that returned a soft bounce, you must manually resend it from your application. Before the system returns a soft bounce such as “mailbox full,” “too busy,” or “network error,” it automatically attempts to resend the message up to five times over a four hour time period.

An email message may return a soft bounce failure if the recipient's mailbox is full or exceeds its maximum storage. A soft bounce of Mailbox Full may indicate one of several conditions.

  • The recipient may have received an unusually high volume of email, or may not have checked email in a while due to vacation or travel. We recommend you attempt to resend the message and monitor its acceptance status.

  • As consumers average three separate email accounts, a Mailbox Full failure may signify an email account of lesser importance. We recommend you attempt to contact the recipient through alternate means to request new or updated email address information.

  • The recipient may have abandoned the email address. We recommend you monitor for a hard bounce failure of Closed in response to future mailings. If this occurs, you should contact the recipient through alternate means to request new or updated email address information.

An email message may return a soft bounce failure if the recipient's account is inactive or temporarily disabled. A soft bounce of Inactive/Disabled Account may indicate one of several conditions.

  • The recipient may not have paid the subscription fee or is involved in a dispute with the mailbox provider. We recommend you attempt to resend the message and monitor its acceptance status.

  • The recipient may not have checked email in a while due to vacation or travel. We recommend you attempt to resend the message and monitor its acceptance status.

  • The mailbox provider may have flagged the account as inactive due to lack of use, or the recipient may have abandoned the email address. We recommend you monitor for a hard bounce failure of Closed in response to future mailings. If this occurs, you should contact the recipient through alternate means to request new or updated email address information.

An email message may return a soft bounce failure if it has been greylisted. The greylist is a temporary block used by smaller ISPs and corporate domains to combat SPAM. When a message is greylisted, the recipient's mail server does not reject the message; instead, it tests to see if the sender will attempt delivery again as a means to filter out SPAM. We recommend you attempt to resend the message and monitor its acceptance status.